Crumpled cloth/paper-like black artefacts on render
Is it possible that you are using a Musgrave-noise as input for a bump-node for your surfaces?
If so, you should add a &quot;Clamp&quot;-node in between, as Musgrave can deliver values outside the expected bounds.
(There used to be a great answer with this info some months ago, but I couldn't find it any more to link it here, sorry...)